Bone anchor systems

ABSTRACT

Embodiments of the invention relate generally to tissue anchors and methods of delivering same to the intervertebral disc or other sites within the body. In some embodiments, the anchors provide pull-out resistance, stability and/or maximize contact with tissue involving a minimum amount of penetration. In some embodiments, delivery methods are minimally invasive and include linear, lateral, and off-angle implantation or driving of anchors along, against or within tissue surfaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 13/789,314, filed Mar. 7, 2013, now U.S. Pat. No. 9,039,741, which is a continuation of U.S. application Ser. No. 13/175,278, filed Jul. 1, 2011, now U.S. Pat. No. 8,394,146, which is a continuation of U.S. application Ser. No. 11/641,253, filed Dec. 19, 2006, now U.S. Pat. No. 7,972,337, which claims the benefit of U.S. Provisional Application No. 60/754,237, filed Dec. 28, 2005, the entire teachings of each of which are incorporated in their entirety into this disclosure by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates generally to tissue anchors, delivery methods, and associated treatments. Anchors according to one or more embodiments of the invention can provide superior pull-out resistance, stability and may, in some embodiments, maximize contact with tissue involving a minimum amount of penetration. Delivery methods include linear, lateral, and off-angle implantation or driving of anchors along, against or within tissue surfaces.

Description of the Related Art

Anchors described herein can be used throughout the human body and have general applicability to fastener art. Such anchors can be used to join or anchor like or disparate materials or tissues together, maintain alignment of materials, reinforce a fracture within a material, and provide an attachment site along or within a materials surface. Generally the art includes both staples and screws. For example, U.S. Pat. No. 7,131,973 to Hoffman discloses an anchor and delivery system for treating urinary incontinence. The distal portion of the delivery tool is curved and hooked such that pulling on the instruments handle effects a retrograde delivery of the anchor. U.S. Pat. No. 5,366,479 to McGarry et al. discloses a staple and delivery system. The staple is flat but contains a pair of inwardly curving prongs. U.S. Pat. No. 5,391,170 to McGuire et al. discloses an angled screw driver for inserting bone screws in ligament tunnels as part of a ligament reconstruction procedure. U.S. Pat. No. 5,217,462 to Asnis et al. discloses a screw and driver combination having threaded shank and sleeve that cooperate to hold and release the screw. U.S. Pat. No. 5,002,550 to Li discloses a suture anchor with barbs and an installation tool that includes a curved needle for attaching a suture.

SUMMARY OF THE INVENTION

As described above, tissue anchors exist in the prior art. However, there remains a need for an anchor that can be delivered laterally, provide pull-out resistance, provide stability, and/or maximize contact with tissue involving a minimum amount of penetration. Embodiments of the invention relate generally to tissue anchors and methods of delivering tissue anchors to the intervertebral disc or other sites within the body. In one embodiment, an anchor delivery system is provided. The anchor delivery system can be pre-loaded with an anchor or the anchor can be provided separately. In one embodiment, the invention comprises one or more anchors. In another embodiment, the invention comprises a delivery tool. In yet another embodiment, the invention comprises a delivery system. The delivery system may comprise the delivery tool with or without an anchor.

In one embodiment, the anchor delivery system comprises an anchor and a hollow elongate guide body adapted to retain the anchor. The guide body comprises a proximal end and a distal end and comprises a curved passage or slot terminating in a lateral opening at the distal end. The curved passage or slot is adapted to retain the anchor. A push rod is slidably mounted within the guide body and is operable to contact the anchor in the curved passage or slot via linear advancement of said push rod to laterally drive out the anchor.

The anchor, alone or in combination with the anchor delivery system, according to one embodiment, comprises a bridge having a horizontal and vertical axis. The bridge terminates or substantially ends in at least a first prong and a second prong. The first prong and second prong extend at an angle from the bridge and are curved. The first prong and second prong are parallel along at least a portion of the first prong and the second prong. The first prong and second prong are perpendicular to the horizontal axis of the bridge. In some embodiments, the first and/or second prong comprise distal tips beveled on one or more surfaces. The two prongs can be dimensioned identically or variably. In one embodiment, the beveled tip is sharpened for advancement into bone so that a pilot hole need not be drilled.

In some embodiments, the anchor delivery system comprises an alignment means for aligning the lateral opening with a tissue surface. In other embodiments, the anchor delivery system comprises an engagement means to engage tissue. In yet other embodiments, the anchor delivery system comprises teeth, spikes, barbs, protrusions, friction plates, or combinations thereof.

In alternative embodiments, the anchor delivery system comprises a biologically active or therapeutic agent. A portion of the anchor or delivery tool may be impregnated or coated with a biologically active or therapeutic agent in some embodiments.

In several embodiments, the anchor delivery system comprises a prosthetic device. In other embodiments, the anchor is coupled to a prosthetic device.

In one embodiment, the anchor delivery system or the anchor is operable to be coupled to an intervertebral disc anulus or nucleus augmentation device, or both.

In one embodiment, the anchor delivery device comprises a guide body having a length in the range of about 5 cm to about 50 cm, preferably 10 cm to about 30 cm and a width in the range of between about 0.1 cm to about 5 cm, preferably 0.5 cm to about 1.5 cm.

In one embodiment, the push rod has a length in the range of about 5 cm to about 70 cm, preferably about 15 cm to about 40 cm and a width in the range of between about 0.01 cm to about 5 cm, preferably about 0.1 cm to about 1 cm.

In one embodiment, the first prong and the second prongs have heights in the range of about 0.1 cm to about 10 cm, preferably about 0.2 cm to about 5 cm. Widths in the range of between about 0.01 cm to about 2 cm, preferably about 0.05 cm to about 0.5 cm, are provided. In several embodiments, a third, forth, or fifth prong is provided. In some embodiments, more than five prongs can be used. Prongs can be of identical height and width or have dimensions different from one another. In one embodiment, a fork-like device is provided, with each tine have a different height. In other embodiments, at least two of the tines have different widths or heights. In other embodiments, the prongs are dimensioned identically. In alternative embodiments, prongs or tines may have different flexibilities. A single prong or tine may be variably flexibly along its length. Variation in tine or prong dimensions or rigidity may be well-suited to certain environments that have variable tissue types, depths, strength, fragility, or flexibility.

In one embodiment, the bridge has a length of about 0.01 cm to about 10 cm along its horizontal axis, preferably 0.1 cm to about 5 cm.

In several embodiments, the anchor is at least partially constructed from a material selected from the group consisting of one or more of the following: nickel titanium alloy, titanium, cobalt chrome alloys, steel, or combinations thereof.

In several embodiments, methods of delivering an anchor according to any of the embodiments described herein are provided. In other embodiments, the invention comprises a minimally invasive method of treating a mammal with an anchored prosthetic.

In one embodiment, a method of delivering an anchor along the surface of a tissue is provided. In one embodiment, the method comprises providing a delivery device comprising an elongate guide body having a proximal and distal end and a push rod slidably mounted within the guide body. The guide body has a curved passage or slot terminating in a lateral opening at the distal end of the guide body. A curved anchor is inserted into the curved passage or slot. A distal end of the guide body is inserted along the tissue surface. The push rod is pushed to laterally expel the curved anchor into the tissue surface along a curvilinear trajectory. The curvilinear trajectory comprises an angle in a range between about 45 degrees to about 135, preferably about 75 degrees to about 100 degree, relative to the tissue surface.

In one embodiment, the tissue surface comprises bone, such as a vertebral endplate.

In one embodiment, the step of inserting a distal end of the guide body along the tissue surface comprises distracting opposing vertebral bodies.

In another embodiment, the method further comprises providing a depth stop on the guide body operable to limit the depth traveled by the distal tip and aligning the depth stop against an outer surface of the tissue.

In another embodiment, a method of providing an anchor within a surface is provided. The method comprises identifying a first surface adjacent to second surface wherein the surfaces are offset relative to each other and form an intersection defining a corner or angle. An anchor with an elongated plate-like keel portion having a length defined by a leading edge and trailing end and having a height defined by a lower edge of the keel is provided. The anchor also has a neck extending from the upper surface of the keel where the neck further comprises an attachment site. The anchor is positioned relative to the intersection such that at least a portion of the attachment site of the anchor is flush or beyond the intersection and at least a portion of the leading edge is adjacent the first surface. The leading edge is driven into the first surface while simultaneously advancing the attachment portion across the second surface.

In one embodiment, the method further comprises providing a bifurcated keel forming an apex at the intersection with the neck. In another embodiment, the method further comprises advancing the anchor beyond the surface of the first surface thereby countersinking it. In yet another embodiment, the method further comprises positioning at least a portion the neck above the intersection.

In one embodiment, the method further comprises identifying two surfaces that are substantially perpendicular. The first surface can be the exterior of a vertebral body and the second surface can be the corresponding adjacent vertebral endplate.

In one embodiment, an anchor comprising an elongated plate-like keel portion having a length defined by a leading edge and trailing end and having a height defined by a lower edge of the keel is provided. The anchor may comprise a neck extending from an upper surface of the keel. The neck may comprise one or more attachment sites.

In another embodiment, the invention comprises an anchor comprising a neck terminating in one or more plate-like keel portions having a length defined by a leading edge and trailing end and having a height defined by a lower edge of the keel and a top portion of the neck. The neck may comprise one or more attachment sites.

In yet another embodiment, the cross-section of the anchor is shaped like an “upside-down Y.” The anchor comprises a neck terminating in two or more plate-shaped or plate-like keel portions having a length defined by a distance separating a sharpened leading edge and trailing end and having a height defined by a lower edge of the keel and a top portion of the neck. The keels form an angle between about 5 degrees to about 360 degrees, preferably about 10 degrees to about 180 degrees, more preferably about 90 degrees at the termination of the neck. The neck comprises an attachment site and extends along at least a portion of the length of the keel. In some embodiments, the plate shaped keel portion appears as an ovoid or substantially circular shape. In some embodiments, the keel portion comprises a wire frame or mesh.

Although one anchor is provided in some embodiments, two, three, four or more anchors are used in alternative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B show an axial and sagittal view of a spine segment and various anchor sites.

FIG. 2 shows an exploded view of one embodiment of a curvilinear anchor and delivery instrument.

FIG. 3 shows a perspective view of one embodiment of a curved two pronged staple type anchor.

FIGS. 4A-E show a sequence involving loading an anchor into a delivery instrument and forcing it out of the lateral opening at the distal end of the delivery instrument according to one embodiment.

FIG. 5 shows an exploded view of one embodiment of a delivery instrument and detachable sleeve.

FIGS. 6A-G show a delivery sequence involving a vertebral endplate according to one embodiment.

FIG. 7 shows a prior art bone screw and intervertebral anatomy.

FIG. 8 shows an embodiment of an anchor according to one or more embodiments of the invention.

FIG. 9 shows another embodiment of an anchor according to one or more embodiments of the invention.

FIG. 10 shows another embodiment of an anchor according to one or more embodiments of the invention.

FIG. 11 shows one embodiment a delivery tool.

FIG. 12 shows the delivery tool in the previous figure with an anchor mounted

FIG. 13 shows an axial cross sectional view of a vertebral body and implanted anchor.

FIGS. 14A-B show an expanded view and a frontal view of the implanted anchor in the previous figure.

FIG. 15 shows a sagittal view of the implanted anchor in the previous figures.

FIG. 16 shows an axial cross sectional view of a vertebral body and a delivery tool inserted along an endplate in the vicinity of an anulus defect or anulotomy.

FIG. 17 shows an axial cross sectional view of a vertebral body wherein an anulus reinforcement device has been implanted along and within the anulus and is attached to an anchor embedded within the vertebral body.

FIGS. 18A-C show various views and features of anchors according to one or more embodiments of the invention.

FIG. 19 shows various profiles of the keel portion of one or more anchors.

FIG. 20 shows a perspective view of another embodiment of an anchor according to one or more embodiments of the invention with a plate-like attachment means suitable for three sutures.

FIG. 21 shows a perspective view of another embodiment of an anchor according to one or more embodiments of the invention with an “eye” attachment means.

FIGS. 22A-B show embodiments of the anchor and delivery tool. FIG. 22A shows a perspective view of another embodiment of an anchor according to one or more embodiments of the invention having a three legged keel portion and designed such that only the attachment portion remains proud on the tissue surface. FIG. 22B shows a delivery tool for driving an anchor with a mated surface and alignment pins.

FIGS. 23A-B show a perspective view of another embodiment of an anchor according to one or more embodiments of the invention having a flexible linkage member.

FIGS. 24A-C show a series of perspective views of one embodiment of an anchor and barrier system according to one or more embodiments of the invention.

FIGS. 25A-C show a series of perspective views of another embodiment of an anchor and barrier system according to one or more embodiments of the invention.

FIGS. 26A-B show a side view and perspective view of an anchor with a sharpened leading edge having a recessed region corresponding to the cupped cortical rim of a vertebral endplate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the invention relate generally to tissue anchors and methods of delivering tissue anchors to the intervertebral disc or other sites within the body. In some embodiments, the tissue anchors provide pull-out resistance, stability and/or maximize contact with tissue involving a minimum amount of penetration. In some embodiments, delivery methods are minimally invasive and include, but are not limited to, linear, lateral, and off-angle implantation or driving of anchors along, against or within tissue surfaces. In several preferred embodiments, bone anchors are provided.

The term “anchor” as used herein shall be given its ordinary meaning and shall also include, but not be limited to, nails, staples, screws, fasteners, sutures, spikes, tacks, keys, pegs, rivets, spikes, bolts, and pins. In several embodiments, the anchor comprises one or more tines or prongs. In one embodiment, the anchor is forked. In some embodiments, the anchor may be straight, curved, or partially curved.

In several embodiments, the anchors disclosed herein are particularly suited for hard tissues such as bone. In other embodiments, soft tissue anchors are provided. One or more embodiments of the anchor can be delivered into a tissue and be secured within said tissue and resist extraction, migration, and/or rotation. Such stability is especially important in environments like the spine, where the anchor is adjacent delicate nerve tissue such as the spinal cord. However, in several embodiments, the anchoring system may be used in other delicate vasculature such as the aorta.

Although several examples of sites appropriate for anchors are described herein for use in the boney tissue of the spine and particularly the vertebral endplates, anchors according to the embodiments described herein have broad applications. For example, the anchors described herein may be used in the radial head, ulnar head, humeral head, tibial plateau, scapula, acromion, talus, malleolus; tendons and ligaments such as the talo-fibular ligament, anterior cruciate ligament, patella tibial tendon, achilies tendon, rotator cuff, and other tissues such as the meniscus. Further, anchors according to one or more embodiments of the invention can disposed within artificial tissues or prosthetics.

FIG. 1A provides a sagittal view of a spine segment. Also shown are numerous potential anchor sites and are marked as “X.” FIG. 1B is an axial view of the same spine segment and shows other possible anchoring sites including along or within a vertebral body, endplate, transverse process, spinous process, facet, and pedicle. In other embodiments, an anchor can be placed along the cortical rim of the endplate or medially within the cancellous bone or relative to or within a pedicle, skull, or sacrum. Other anchoring sites include, but are not limited to: relative to a defect within the disc either in the area of the defect, at the interface of the anulus and nucleus or in the area of the nucleus.

In several embodiments, one or more anchors are used in connection with an anulus or nucleus augmentative device, as described in U.S. Pat. Nos. 6,425,919; 6,482,235; 6,508,839; and 6,821,276, all herein incorporated by reference. In one embodiment, one or more anchors are used to anchor an anulus augmentation device that is placed within or beyond a defect in the anulus to the vertebral endplates.

One or more embodiments of the invention comprise anchors made at least partially of one or more of the following materials: any biocompatible material, material of synthetic or natural origin, and material of a resorbable or non-resorbable nature. The anchor may also be partially or wholly constructed from material including, but not limited to, autograft, allograft or xenograft; tissue materials including soft tissues, connective tissues, demineralized bone matrix and combinations thereof; resorbable materials including polylactide, polyglycolide, tyrosine derived polycarbonate, polyanhydride, polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite, bioactive glass, collagen, albumin, fibrinogen and combinations thereof; and non-resorbable materials including polyethylene, polyester, polyvinyl alcohol, polyacrylonitrile, polyamide, polytetrafluorethylene, polyparaphenylene terephthalamide, cellulose, and combinations thereof. Further examples of non-resorbable materials include carbon-reinforced polymer composites, shape memory alloys, titanium, titanium alloys, cobalt chrome alloys, stainless steel, and combinations thereof. In some embodiments, the anchor comprises titanium alloys or cobalt chrome.

In several embodiments, the anchor comprises an anchor body and an anchor attachment site. In one embodiment, the anchor attachment site is adapted to accept or connect to a suture, linkage element, threaded screw, or provide a surface for ingrowth into an adjacent structure. The anchor attachment site can be integral to the anchor or a separate structure comprised of the same or different material as the anchor body. The anchor attachment site can be coupled to the anchor body. For example, the anchor attachment site can be flexibly, rigidly, or rotationally connected to the anchor body.

The anchor attachment site can comprise one or more of the following structures: head, flange, plate, disc, protrusion, channel, hole, cleat or eye. These structures can be placed at various positions along the anchor. For example, one or more of these structures may be placed at or near the ends of the anchor, in the middle of the anchor, or at any other desired position. In some embodiments, the anchor attachment site comprises mesh, fabric, or membrane material, or a combination thereof. The site may be parallel, perpendicular or angled with respect to the body of the anchor. In one embodiment, the anchor attachment site is located on an end or terminus of the anchor body.

In one embodiment, the anchor comprises one anchor body and one anchor attachment site. In another body, the anchor comprises one or more anchor bodies and one or more anchor attachment sites. In one embodiment, the anchor comprises one body and two attachment sites.

In one embodiment, at least a portion of the anchor comprises a biologically active or therapeutic agent. For example, in some embodiments, at least a portion of the anchor can comprise growth factors such as bone morphogenic proteins, insulin-like growth factor 1, platelet derived growth factor, and fibroblast growth factor. In one embodiment, both the anchor body and anchor attachment portion of the anchor can be adapted to deliver a biologically active or therapeutic agent. In other embodiments, at least a portion of the anchor is coated with a biologically active or therapeutic agent.

Curvilinear Anchor

Anchors (including staples, nails, and other fastening or joining devices) according to one or more embodiments of the invention can be partially or wholly arcuate or curvilinear. The radius of curvature (the tightness or gentleness of the curve) can vary among embodiments as can the section of a circle corresponding to the anchor. For example, an anchor having a 90 degree curve would appear as ¼ of a circle. Other ranges of curves between 0-180 degrees are also possible. In some embodiments, for example, the curvature is about 15, 30, 45, 60, 75, 90, 120, 150, or 180 degrees.

An anchor can also be at least partially curved with a linear portion extending upward. In this embodiment the curved portion is adapted for driving into a tissue and the straight portion remains proud, or above the surface. Depending upon how the anchor is driven into the surface, the proud portion of the anchor can be anywhere from 0-180 degrees relative to the surface. The curvature of an embodiment of the anchor can also be variable along the anchor. Such a variable curvature could be employed to increase or decrease pressure on tissues adjacent to the anchor. In one embodiment, the proud portion is about 15, 30, 45, 60, 75, 90, 120, 150, or 180 degrees relative to the surface.

The surface or body of the anchor can be roughened, porous, barbed, lubricated, coated or impregnated with a biologically active or therapeutic agent. The anchor can be in the form of a curved nail or staple with a crown or bridge and having two or more prongs or legs extending therefrom. A slot or gap between the prongs in one ore more embodiments of a staple can be aimed at a suture or other structure already implanted in or along a surface and then hammered in place thereby anchoring the suture in place. The tips of the prongs of a staple can be beveled to effect a wedging action. By beveling or angling the inner, outer, front, and/or back of a prong tip, the prong will tend to travel in a particular direction. Moreover, the beveled tips can complement each other, work in opposition, or some combination thereof. In one embodiment the prong tips are beveled on the outside edge, in another embodiment the tips are beveled on the inside edge. In yet another embodiment, the top of one prong is beveled and the bottom of another is beveled. In addition, the cross section of prongs may be variable along the length of the anchor. In one embodiment, the anchor prong's smallest cross section is at or near the tip and at its greatest furthest from the tip, creating a wedge along the curve of the anchor. This may aid in increasing compression on all or part of the bone or other tissue in contact with the anchor.

In another embodiment of the invention, an anchor can be resiliently flexible such that after passing through a curved slot or deflecting surface of the delivery device, the anchor (including staples, nails, etc) straightens out to its original shape as it is advanced out of the device and into the tissue. The original shape, predetermined shape, first shape, or unrestrained shape can be, for example, straight, angled, corkscrew, or offset. The prongs or legs of one or more embodiments of the anchor, such as, for example, a staple, can be straight, curved, angled, corkscrew, or offset with respect to each other.

Anchor Delivery Tool

Turning now to FIG. 2, shown is a preferred embodiment of an anchor and delivery instrument according to one or more aspects of the invention. A guide body 4 has a cylindrical grip or hand hold and first proximal and second distal end. The body 4 can be partially or fully hollow and contain a guide way chamber 5 for holding and orienting an anchor or staple 3 terminating in an opening at the distal end of the guide body. The opening can be oriented axially out of the front of the body or laterally and side mounted. The guide way chamber 5 comprises a curved or angled slot or passage and opens perpendicular or off angle (or between 0-180) with respect to the long axis of the guiding body. The radius of curvature along the passage can be constant or variable along the sweep of the curve. A curved nail or staple 3 can be inserted within the chamber 5 via a side loading window. A pusher rod 1 is carried within or by the body 4 and accesses or is in communication with the guide way chamber. The rod 1 has a first proximal end that can be configured with a head or striking surface for hammering and a second distal end for transmitting force to the end of a nail, staple, or anchor 3 within the guide way chamber 5. The distal end or anvil can be curved, beveled, or angled such that the linear force of the rod can be transmitted downward or along an arc as the staple 3 is driven out through the curved slot of the chamber 5. The rod 1 may be rigid or at least partially flexible in construction.

Also shown in FIG. 2 is a depth stop support 2 which can be configured as a snap on sleeve that fits over the body 4. In other embodiments a depth stop may simply be a projection off of the body that limits further travel of the body and/or guide way chamber opening within or adjacent a tissue. The depth stop may also be adjustable to allow for different implantation depths or locations. The depth stop may project in one or more directions from the long axis of the tool. Depth stops and other instrumentation described in U.S. Pat. No. 6,821,276, herein incorporated by reference, may be incorporated in several embodiments of the invention.

FIG. 3 is an example of an embodiment of a staple or anchor 3 with two prongs or legs that are barbed and beveled on the outside. When the staple is driven into a surface such as a bone the prongs may or may not bend inward or be wedged together. This action will pinch and compress the bone tissue between the prongs while pressing outwardly against the sidewalls of the bone facilitating a stable anchorage.

The series depicted in FIGS. 4A-E shows an embodiment of a delivery device being loaded with and anchor and the push rod applying force to the anchor and partially driving it out of the curved guide way chamber opening or lateral opening. FIG. 4 B also shows the depth stop support sleeve 2 with a vertical slot corresponding to the guiding body distal slot which is aligned with the midline of the anchor and can be used to precisely implant or drive the anchor or staple around a suture or linear structure.

In FIG. 5, an embodiment of the depth stop support is shown as an attachable sleeve that fits on or over the distal end of the guiding body. However, many of the features of the sleeve can be machined, welded or attached directly to the body if so desired. In addition to the vertical slot corresponding to the guiding body distal slot and adjustable depth stop, an alignment projection 8 is shown. The alignment projection can form a right angle with the depth stop and have a beveled tip to ease insertion. The alignment tip can be a relatively flat and rectangular projection that in use can be rotated and rocked between to vertebrae or a hole in an anulus to distract the vertebrae. Upon partial or full distraction the tip and at least part of the guiding body can be inserted between the adjacent vertebral bodies. The depth stop can limit the amount of insertion by catching the edge of one or both of the opposing vertebral endplates. Vertebral taxis or the resistance of the anulus and endplates to further distraction can serve to immobilize the guiding body as the anchor is hammered out. Alternatively the body can be wedged along an inferior superior plane to drive the opening of the guide way chamber against the desired anchor site. In another embodiment one or more depth stop surfaces may contain one or more barbs, spikes, nails, fasteners, or means for engaging or immovably coupling the distal end of the body to a boney structure such as a vertebral body. In one embodiment an upper depth stop surface may be configured to engage a superior vertebral body and a lower depth stop surface may be configured to engage an inferior vertebral body.

Although the push rod and hammering method described infra is a preferred method of delivery other methods and devices can be used for this purpose. For example, compressed gas and hydraulics can be utilized for driving. The push rod can be configured as a piston or threaded rod (that can be rotated to expel the implant) for imparting linear force. Also, the threaded rod or piston can be flexible or have joints along its length to accommodate a curved or flexible guiding body.

Delivery instruments and devices according to one or more embodiments can also be used to implant other devices besides anchors and the like. For example, a prosthetic device (including, but not limited to, a barrier, mesh, patch, or collapsible implant) can be attached or coupled to an anchor according to several embodiments of the present invention, such as described in U.S. Pat. Nos. 6,425,919; 6,482,235; and 6,508,839; 6,821,276, all herein incorporated by reference. In several embodiments, the prosthetic device can be loaded within or along the guiding body of the device. The anchor and the prosthetic device may be constructed from identical, similar, or different materials. The anchor and prosthetic device may be coupled or removably or reversibly. Connections between the anchor and the prosthetic device may be temporary (such as restorable or dissolvable sutures) or permanent. Instead of a prosthetic device that is coupled or attached to the anchor, the prosthetic device may also be of unitary construct or integral with the anchor.

In one embodiment, an implant such as collapsible patch is coupled to the anchor and oriented along or within the guiding body such that as the anchor is passed through the guide way chamber slot in a downward direction the patch is extruded outwardly or parallel to the long axis of the body. The patch can be held within the body which can have linear slot adjacent the curved slot of the guide way chamber or alternatively the patch can be mounted around the guide way chamber while coupled to the anchor within the chamber. Also, the depth stop sleeve can also be used to compress and hold the patch in place.

In a further embodiment, one or more anchors can be delivered separately from one or more implants. In one embodiment, the implant is first delivered and positioned and then anchored in place. In another embodiment, the anchor is first established in the implantation site and then the implant is delivered and connected to the anchor.

FIGS. 6A-L depicts an implantation sequence according to various embodiments of the invention. FIG. 6A is an axial cross section of a vertebral body, shown is a star shaped treatment zone along the vertebral endplate. The sequence shows an anchor being implanted into a posterior portion of a vertebral body along an endplate. The surface of the endplate can be accessed through a hole in the anulus. The hole in the anulus may be a naturally-occurring defect or surgically created. Methods and devices according to the invention are not limited to a single location along a vertebral body or surgical approach.

Perpendicularly Driven Anchor

Various embodiments of anchor presented herein are designed to improve upon the weaknesses in conventional bone screws and staples that are limited by surgical access and suture or anchor attachment site placement. For example, in the environment of the spine, the posterior elements of vertebral bodies forming facet joints, spinal canal, neural foramen, and the delicate nerve tissues of the spinal cord create numerous obstacles for surgery and diagnostic and interventional methods. Surgical approaches have been adapted to minimize damage to these structures and involve tight windows usually off angle to the target tissue.

An example of such prior art anchor and environment is depicted in FIG. 7, which shows a bone screw driven into a vertebral body from a posterior lateral approach. Here the anchor on the outside of the vertebral body is ineffective for retaining an implant within the disc and remains in dangerous proximity to the spinal cord. Several embodiments of the present invention are particularly advantageous because the anchor does not present attachment sites originating at a proximal end in the axial orientation from which they are driven. Moreover, several embodiments of the present invention are advantageous because the anchor is adapted with an expansion mechanism that provides a “mushrooming” effect, and thus the pull-out resistance is not merely limited to the friction and forces generated by the sidewalls of the material or tissue.

Several embodiments of the presentation invention accommodate or exploit certain geometries or anatomical structures of the body. For example, in one embodiment, the attachment site of an anchor can be presented distally from the insertion site in a direction perpendicular or offset from the axial orientation of insertion. In one embodiment, the anchor presents a larger surface area below or embedded within a surface, thereby offering improved pull-out resistance without requiring an expansion or “mushrooming” step or mechanism.

In several embodiments, one or more anchors are driven into the surface of a first plane and present a portion on an adjacent plane or surface perpendicular or angled relative the first plane. Thus, the anchor is driven into a first surface and across an adjacent surface in the same instance. In one or more embodiments, at least a portion of the anchor such as the anchor attachment site is adapted to remain above or proud of the upper or second tissue surface or plane. With respect to the first surface (the front facing or lower surface into which the anchor is driven), the anchor can be driven in to a depth such that it is countersunk, left flush, or left partially external to the frontal tissue surface or plane. The anchor can also be delivered at a trajectory or angle relative to the second or top surface such that it is driven into the first surface and downwardly or upwardly across the second surface.

In several embodiments, the anchor is a flat plate-like nail or brad having a specialized keel portion and neck portion. In other embodiments the anchor is flat, plate-like, curved, corrugated, round, or a combination thereof. The neck can be terminated in a head or present an attachment portion along its length. The attachment portion or site can be comprised of a more flexible piece of fabric, wire, linkage, fastener component, hook eye, loop, or plate. The neck can be an extension, ridge, midline, or the apex of the keel portion. The neck can be oriented at the distal or proximal end of the keel or anywhere along its length. The neck can be the same length as, longer than, or shorter than the keel but preferably it is shorter. In one embodiment, the neck is a thin rod or beam. The keel portion can have a cross-section similar to a wedge, “V”, “U”, “T”, “W”, “X” and other shapes.

Anchors according to one or more embodiments of the present invention have dimensions suitable to the implantation environment. For example, in one embodiment, the anchor has a height of about 0.2 cm to about 5 cm and a width of about 0.2 cm to about 5 cm. Anchors can have a length or depth from 0.2 cm to about 5 cm. In some embodiments, the length, width, height or depth can be less than 0.2 cm or greater than 5 cm. In one embodiment, the anchor has a length of about 1 cm and a width of about 0.5 cm. In yet another embodiment, the anchor has a length of about 0.5 cm and a width of about 0.25 cm. In another embodiment, the anchor is dimensioned as follows: about 0.3 cm wide, 1 cm long and 0.5 cm deep.

The length of the anchor can define a straight or curved line defined by a radius of curvature of about 0-90 degrees (e.g., about 15, 30, 45, 60, or 90 degrees). The keel, legs, extensions, blades, or fins can have a leading edge that is sharpened, left dull, or serrated. Other features of the neck and keel or extensions include, but are not limited to, barbs, tabs, roughened surface geometry, polished surface, coatings seeded carrier or drug eluting coatings or elements, concavities, scalloped ridges, grooves, “feet”, ridges, voids, slots, and ingrowth openings are shown in the attached drawings. Secondary edges or ribs can protrude along portions of the keel to provide enhanced engagement with tissue.

In addition to the neck and anchor attachment site, the anchor can also include an alignment means, engagement means or guide. Variations of the anchor alignment means can function to orient the anchor to a driver and couple it thereto. The anchor alignment means can comprise alignment components such as a protrusion, recess, or fastener component mated to a portion of a delivery instrument. The anchor engagement means can comprise engagement components or portions such as spikes, teeth, prongs, barbs, friction zones, or a combination thereof. The guide can comprise a protrusion, slot, arrow, tab, or a combination thereof. Thus, in some embodiments, the anchor comprises means to align, means to engage, means to guide, or a combination thereof.

Turning to the drawings, FIG. 8 shows an embodiment of an anchor 25 with a leading edge 12, suture attachment sites 11, ingrowth features or voids 13, first and second plate-like legs or lateral extensions 15, 15′ defining the keel, arcuate central ridge or apex 10, centering or alignment projection 16, and feet or ridges 14, 14′. Both the wedge-like shape of the keel portion of the implant i.e., the legs and the ridges or flange like extensions at the end of the legs function to hold the implant within a given tissue and to resist rotation and pull out from a variety of angles. The voids and ingrowth features serve to provide secondary stabilization over time and/or to allow chemical transfer or cellular respiration across the implantation site.

In a “V” shaped anchor or similar embodiment shown, the neck portion is bifurcated into two legs, extensions, blades, fins, or keels that meet at an apex and form an angle between about 10 and about 170 degrees. In one embodiment, the angle is about 30-90 degrees. The apex at the point of bifurcation can define a flat ridge or vertical extension or neck that can contain one or more anchor attachment sites. In a “U” shaped embodiment the neck can be in the form of an arc or eye projecting along the length of the body of the anchor. “V” or “U” shaped anchors can be modified to “L” shaped anchors in some embodiments.

In FIG. 9, an anchor similar to the one depicted in the previous figure is shown. The apex 10, which would correspond to the neck in other embodiments, does not extend and instead presents a smooth curve which can present a less injurious profile to the anatomy in certain applications. Also shown are ridges 70 and scalloped teeth-like surface features 71.

FIG. 10 shows another embodiment of an anchor with deployed barbs 80 and 80′ These features can be held compressed within a sleeve on a delivery instrument or simply forced to compress inwardly as the implant is driven in to tissue. One or more slots or recesses 82 are adapted for holding the barbs during implantation to streamline the anchors profile.

One or more barbs can exert continuous outward pressure on the sidewalls of a tissue or expand to their maximum and form a shelf or flange if the tissue geometry widens, expand or become more pliant. For example, in a vertebral body the implant might be driven into cortical bone and then further into cancelous bone. Upon reaching the cancelous bone, the barbs flexible plate-like structure or engagement means, can expand or extend outwards. In another example the anchor is driven at least partially into the hollow of a boney structure such that the barbs expand and engage the inner wall of the bone. Element 83 is an opposing barb or expansion means however one or more barbs can be oriented relative to each other from 0-360 degrees. For example, the barbs or other barb-like components may be orientated relative to each other at the following angles: 15, 30, 45, 60, 90, 120, 150, 180, or 360 degrees.

FIG. 11 shows a delivery tool with a shaft 96 with distal end 95 having an anvil or striking surface 94 defining a leading edge mated to at least a portion of the cross section of the trailing edge of the anchor. The shaft may be connected at its proximal end to a handle or terminate in a striking surface. Because the anvil surface is similar to the anchor in some embodiments, both the anchor and at least part of the distal end of the delivery tool can be driven into a bone thereby counter sinking it. Alternatively, anchors according to one or more aspects of the invention can be left flush or partially countersunk. A mounting member 90 may extend beyond the implant when the implant is mounted or loaded on the tool. The mounting member 90 includes a flattened lower surface 93 and a rounded blunt front surface 91 for positioning along a bone surface, such as the top of a vertebral endplate, and a slot or engagement means 92 for accepting an aligning an anchor.

FIG. 12 shows the anchor 25 mounted on the mounting member 90. The extended lower surface 93 and the leading edge of the implant 12 and 12′ forms a means to engage bone or other tissue. In one embodiment, the tissue (e.g., bone) engagement means comprises a device having an angled surface that may be used to hook onto, engage, or align the instrument with the edge of a vertebral body or the intersection of two tissue planes. In one embodiment, the engagement means can be used to align the implant with the top of a vertebral endplate and its front outer surface, the anchor is then driven into and across the endplate.

FIG. 13 shows a cross-section of a vertebral body 24 having an anulus fibrosus 23 bounding nucleus pulposus 22 with an anchor 25 embedded into a posterior aspect of an endplate and within or proximal to an anulotomy or defective region of the anulus fibrosus 23. This implantation site is also in the vicinity of the cortical rim or ring of dense bone of the vertebral endplate. The anchor is shown countersunk into the bone along the P-A axis but partially proud along the inferior-superior axis (the dotted lines indicating the portion of the implant below bone surface or level.

FIG. 14A is an expanded view of FIG. 13 and shows dotted lines to represent the keel portion of the anchor 25 beneath the endplate surface. FIG. 14B is a dorsal view of FIG. 14A showing anchor 25.

In FIG. 15, a sagittal view of an implanted anchor 25 is shown at least partially within the defect 33 and inferior vertebral body 32. Superior vertebral body 31 is also shown. The cross-section of the vertebral bodies depicts the denser and thicker bone at the edge or rim where the anchor is implanted and the less dense cancellous bone within the vertebral body.

FIG. 16 depicts a method of delivery for one embodiment of the anchor and associated delivery tool. Shown is a top cross sectional view of a vertebral body 24 and a delivery instrument 44 and an anchor 25. The delivery instrument or driver is used to transmit the force of a hammer or other means to drive the anchor in place. The driver can comprise a slot, holder, magnet, pins, mateable surfaces, fastener or other means at its distal end to engage or couple with the anchor. The anchor can also be attached to the distal end of the driver and then released once the desired delivery depth has been attained. Other features of a driver (not shown in FIG. 16 can include a depth stop, bone engagement means such as a spiked, hooked, or angled protrusion, and/or a retractable sleeve to protect adjacent anatomy as the anchor is positioned. FIG. 16 also shows a flat proximal end 1602 for hammering, if needed and a knurled handle 1600.

Turning to FIG. 17, a top cross-sectional view of an anulus repair implant 51 lying along the inner surface of the posterior anulus is coupled, attached, or sutured 52 to an anchor 25. The connection between the anchor and implant can be permanent or detachable. The implant 52 can be delivered and positioned prior to, at the same time as, or subsequent to the implantation of the anchor 25. FIGS. 17A-17C show various features of anchors.

In FIG. 18A, the surface level of a bone such as a vertebral endplate is shown as a dotted line. A side view is depicted. Here the leading edge of the keel or leg portion of the implant is thinner than the trailing edge. Accordingly, in other embodiments of anchors according to the invention at least a portion of the leading edge, profile, proximal edge or side of an implant can have a thinner or tapered profile than an opposing end, distal end, or trailing edge or profile. FIG. 17B shows a series of anchor variations from a side view in which the top portion, apex, neck, or implant attachment site 170, 171, 172, 173, 174 is symmetrical, rounded, wedge shaped, oriented at the distal or proximal end of the anchor. FIG. 18C shows another side view along the bone surface level depicting and anchors with features discussed infra such as a serrated leading edge, voids or ingrowth holes, and a recess for engaging a delivery tool.

FIG. 19 shows various embodiments of the anchor cross-sections including several keel profiles from a front view resistant to pullout and offering various surface areas. Some are solid shapes as in anchor profiles 182, 184, 187, and 200 and others are hollow and have an open midsection as in anchor profiles 183, 185, 188.

Turning to FIG. 20, a perspective view of an anchor is shown with leading edges 12, 12′, alignment means 16, suture or fastener attachment 11 site or neck 10, and voids 13. In this embodiment the apex does not run the entire length or depth of the anchor corresponding to the keel or opposing leg portions 15, 15′ of the anchor. Also, the neck is oriented towards the proximal end of the anchor forming a cut-out along the top portion of the anchor. The neck 10 is shown perpendicular to the keel 15 but can be alternatively oriented in a range from 0-180 degrees relative to it. In one embodiment, the neck is oriented at an angle of about 15, 30, 45, 60, 75, 90, 120, 150, or 180 degrees relative to the keel

In FIG. 21, a “V” shaped anchor is shown. An “eye” or loop is integral to a neck extension portion 10 that bifurcates into two legs 15, 15′. Because the leading edges 12, 12′ and at least a portion of the neck 10 is sharpened, this anchor can be driven more flush to the upper or first surface of a bone such as a vertebral endplate. Here both the neck 10 and the leg portions 15, 15′ of the device function as a keel. This embodiment also shows ridges 12 and scalloped recesses. Anchors according to other embodiments described herein may also comprise ridges and/or scalloped recesses.

In FIG. 22A, another embodiment of an anchor is shown. Here, three legs defining the keel are provided. A relatively taller neck is provided beneath a perpendicular suture attachment member. The neck 10 is set back distally from the leading edge of the keel portion. FIG. 22B shows the distal tip of a delivery tool. Shown are attachment pins 180, anvil 186 or striking surface, depth stop 187, and mounting member 185.

Turning to FIG. 23A, an anchor 25 is shown with an attachment site for a flexible bridge 188. The bridge 188 is shown in FIG. 23B and is coupled to the neck 10 of the anchor 12 with a first and second flexible tab 193, 194 and has an attachment 11 site at the opposing end.

The series depicted in 24A-24C shows an anulus reinforcement system. FIG. 24A shows an anchor similar to the ones depicted previously with a bifurcated keel 15, 15′, neck 10, and attachment plate 112 with a first and second coupling member 111, 11′ or snap surface. FIG. 24B is an exploded view of a barrier, mesh, or reinforcement plate 52 adjacent an anchor wherein the anchor 25 is partially inserted or mounted within the distal end of a delivery tool. FIG. 24C shows all three elements connected and mounted and ready to be driven into a tissue site.

Another embodiment of an anulus reinforcement system is shown in FIGS. 25A-25C. In this embodiment, a single attachment means 111 is used that can function as a fulcrum or hinge site for a flexible barrier 52 member shown in FIG. 25B. Behind or distal to the attachment means 111 is a support member 112 or plate that is an extension of the neck 10. This feature, in some embodiments, minimizes or prevents the barrier 52 from folding backwards and may also reinforce the barrier 52. FIG. 25C shows a hood or sleeve 120 element that can be mounted on or carried by a delivery tool or instrument as described herein. The hood 120 retains the folded barrier until the anchor portion is fully established within the tissue whereupon it is retracted.

Another embodiment of the invention is shown in FIGS. 26A-26B. This embodiment shows an anchor especially adapted for use in a vertebral body and includes an upside down “V” shaped keel portion with a sharpened leading edge. The leading edges enable the anchor to be directly driven into the bone and do not require a pilot hole or pre-cut. and One feature of this embodiment is the leading step in the sharpened edge which present more cutting surface blow the surface of the bone and more forward of the distal attachment site. Alternatively, the leading edge can have multiple steps or be curved and rounded. This profile reduce the risk that the leading edge might pierce or damage the endplate (which is not flat but has a “dip” or cupped portion in the middle). This feature facilitates insertion of a longer, stronger anchor into a disc that would otherwise (because of a pronounced dip) be difficult to position at the proper height and depth into the bone without damaging the endplate.

Example

The following Example illustrates one embodiment of the present invention and is not intended in any way to limit the invention. Moreover, although the following Example describes an anchor used in a spinal application, the anchors described herein can be used throughout the human body and have general applicability to fastener art. Such anchors can be used to join or anchor like or disparate materials or tissues together, maintain alignment of materials, reinforce a fracture within a material, and provide an attachment site along or within a materials surface.

The anchor illustrated in FIG. 26 is used by way of example. The anchor is in the form of an upside down “Y” defined by a neck portion terminating at one end into two plate-like rectangular legs forming a keel and terminating into an suture attachment site 11 in the form of a loop on the other end. The leading edge of the legs 12 and neck 10 are sharpened and the upper portion of the legs is recessed, profiled or formed with a relief 113. The relief profile 113 can correspond to an anatomical structure, in this embodiment the forward recess or relief 112 corresponds to the concavity or cupping of an endplate. The angle between the keel plates is around 90 degrees. The neck 10 is about 0.1 millimeter high and about 0.2 wide millimeters wide and extends about 0.2 millimeters. The neck 10 and attachment site 11, an “eye” or loop in this embodiment, are mounted at the trailing or aft potion of the keel 15.

The entire structure is made of nickel titanium and is machined from bar stock. To be delivered, the anchor is mounted on the distal end of a driver. The driver has a striking surface on one end and an anvil on the opposing end. The anvil has the identical cross-section as the trailing edge of the anchor and extends about 0.2 cm to allow for countersinking. The anchor is coupled to the anvil by a forked protrusion that holds the neck and a pin that fits into the eye.

In one application, the anchor is used to secure an anulus repair device relative to a defect in the disc. A posterior-lateral approach is used to obtain access to the damaged disc. Part of the posterior elements on the opposing vertebral bodies may have to be removed in order to reach the disc. The anulus repair device is then implanted through the defect and along the inner surface of the anulus.

Next the anchor, which is mounted on the distal end of the driver, is aimed at the top edge or endplate of the inferior intervertebral body. An alignment projection forming a right angle at the tip of the drive is used to align the bottom portion of the attachment loop of the anchor with the upper surface of the endplate and to center the anchor within the defect. The anchor is then driven forward into the bone with light hammering applied to the driver. The anchor is driven roughly perpendicular to the outer surface of the vertebral body and roughly parallel to the endplate.

The depth of insertion is controlled by the 0.2 cm countersinking anvil and the depth dimension of the anchor, in this case 0.5 cm for a total depth of 0.7 cm which is still shy of the border of the cortical rim and the cupping of the endplate. Only the upper portion of the loop remains proud of the endplate surface and the anular repair device can then be connected to it with a suture.

It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. For example, method steps need not be performed in the order set forth herein. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention. 

What is claimed is:
 1. A bone anchor system comprising: a bone anchor configured for insertion into an outer surface of a vertebral body that is perpendicular to an endplate surface of the vertebral body, the bone anchor comprising: a neck, wherein said neck comprises an attachment site along at least a portion of its length; a plate-like keel extending at least substantially perpendicular from the neck and comprising a leading edge, wherein the leading edge of the plate-like keel is configured for advancement within the outer surface of the vertebral body along a trajectory that is at least substantially parallel with the endplate surface, wherein said attachment site is configured to be positioned such that at least a portion of the attachment site remains proud of the endplate surface of the vertebral body upon insertion of the bone anchor, wherein the plate-like keel is configured for countersinking within said outer surface of the vertebral body such that no portion of said bone anchor remains outside said outer surface; and a flexible barrier coupled to the attachment site such that the flexible barrier is proud of the endplate surface upon insertion of the bone anchor.
 2. The system of claim 1, wherein the leading edge of the plate-like keel is sharpened.
 3. The system of claim 1, wherein the plate-like keel comprises friction zones configured for resisting rotation and pull-out of the bone anchor.
 4. The system of claim 1, wherein the attachment site comprises at least one member selected from the group consisting of: a fabric, a wire, a linkage, a fastener component, a hook eye, a loop, and a plate.
 5. The system of claim 1, wherein the flexible barrier comprises a polymer and wherein the bone anchor comprises titanium.
 6. The system of claim 1, wherein the flexible barrier comprises a mesh.
 7. The system of claim 1, wherein a leading edge of the neck is sharpened.
 8. The system of claim 1, wherein the bone anchor is at least partially constructed from titanium.
 9. The system of claim 1, wherein the bone anchor is rotationally coupled to the flexible barrier.
 10. A bone anchor system comprising: a bone anchor configured for insertion into an outer surface of a vertebral body that is perpendicular to an endplate surface of the vertebral body, the bone anchor comprising: a neck, wherein said neck comprises an attachment site along at least a portion of its length; a bone anchoring region extending at least substantially perpendicular from the neck and comprising a leading edge, wherein the leading edge of the bone anchoring region is configured for advancement within the outer surface of the vertebral body along a trajectory that is generally parallel with the endplate surface, wherein said attachment site is configured to be positioned such that at least a portion of the attachment site remains proud of the endplate surface of the vertebral body during insertion of the bone anchor, wherein the bone anchoring region is configured for countersinking within said outer surface of the vertebral body such that no portion of said bone anchor remains exterior to said outer surface; and a reinforcement member coupled to the attachment site such that the reinforcement member is proud of the endplate surface upon insertion of the bone anchor and configured to provide reinforcement to an anulus of an intervertebral disc adjacent the endplate surface.
 11. The system of claim 10, wherein the bone anchoring region comprises a plate-like keel.
 12. The system of claim 11, wherein the leading edge of the plate-like keel is sharpened.
 13. The system of claim 10, wherein the bone anchoring region comprises friction zones configured for resisting rotation and pull-out of the bone anchor.
 14. The system of claim 10, wherein the bone anchor comprises titanium.
 15. The system of claim 10, wherein the reinforcement member comprises a mesh.
 16. The system of claim 15, wherein the bone anchor is rotationally coupled to the mesh.
 17. The system of claim 10, further comprising a delivery tool configured to releasably couple to the bone anchor and to drive the bone anchor into the outer surface of the vertebral body.
 18. A bone anchor system comprising: a bone anchor configured for insertion into an outer surface of a vertebral body that is perpendicular to an endplate surface of the vertebral body, the bone anchor comprising: a neck, wherein said neck comprises an attachment site; a bone anchoring portion extending at least substantially perpendicular from the neck and comprising a leading edge, wherein the leading edge of the bone anchoring portion is configured for advancement within the outer surface of the vertebral body in a direction that is at least substantially parallel with the endplate surface, wherein said attachment site is configured to be positioned such that at least a portion of the attachment site remains proud of the endplate surface of the vertebral body upon insertion of the bone anchor, wherein the bone anchoring portion is configured for countersinking within said outer surface of the vertebral body such that no portion of said bone anchor remains outside said outer surface; and a flexible barrier coupled to the attachment site.
 19. The system of claim 18, wherein the bone anchoring portion comprises a plate-like keel, wherein the bone anchoring portion comprises a friction zone configured for resisting rotation and pull-out of the bone anchor.
 20. The system of claim 18, wherein at least a portion of the flexible barrier is positioned along an inner surface of an anulus of an intervertebral disc adjacent the vertebral body. 